The kinetics of virus-specific IgG and IgM antibody response in patas monkeys experimentally infected with Delta herpesvirus (DHV), was studied using enzyme-linked immunosorbent assay (ELISA). An indirect ELISA (IE) test was used for DHV IgG determination, whereas a "double sandwich" (triple antibody layer) ELISA (DSE) test was found to be very sensitive for DHV IgM detection. In DSE test DHV IgG appeared to interfere with IgM determination only in sera containing DHV IgG levels at least 100 times higher than IgM. IgM antibodies appeared 5-8 days after monkey infection, reached a peak titer in 5-7 days, and after 7 days started to drop in titer and disappeared within two months. IgG antibodies appeared 5 days later than IgM, reaching the plateau in the following 7 days and then remaining stable for at least 2 months. Experimental infection of the patas monkey with DHV appears to be a good animal model for human varicella. IE for IgG and DSE for IgM detection are sensitive ELISA tests for determination of the immune response to DHV infection in patas monkeys.